Supply system for vacuum tubes



Dec. 11, 1934. M pup 1,983,774

SUPPLY SYSTEM FOR VACUUM TUBES Filed Feb. 4, 1924 WITNESSES: INVENTOR ATTORNEY- periodic characteristics.

Patented Dec. 11, 1934 PATENT OFFICE SUPPLY SYSTEM FOR VACUUM TUBES Michael I. Pupin, Norfolk, Conn., assignor to Westinghouse Electric & Manufacturing Compa ly, a corporation of Pennsylvania Application February 4, 1924, Serial No. 690,586

1 Claim.

This application is a continuation in part of my application for a patent on electromagnetic production of direct current with fluctuations, Serial No. 69,566, .filed December 31, 1915.

The invention presented herein relates to a means for supplying direct current to the plate circuits and the filaments of the vacuum devices in radio signalling systems.

It is an object of this invention to utilize a non-uniform source of electro-motive force to supply energy for these circuits and yet produce a uniform current in said circuits.

More specifically stated, this invention has for its object to supply energy to the vacuum tube device of a radio signalling system from ordinary commercial sources of current, such as direct current dynamos or alternating current generators.

Since the current required by such vacuum tubes must be direct, it is obvious that, when the source of supply is an alternating current generator, a rectifier must be used. Ordinarily the current, delivered by a rectifier supplied from an alternating current source,. retains some Periodic characteristics due to the commutator are also present, ordinarily, in current supplied by direct current generators.

It isan object of this invention to provide means for removing the periodic components from the current supplied to the vacuums-tube devices in order that a hum shall not be produced in the telephone receivers associated with the signalling system because of the presence of such periodic currents.

The invention is capable of many modifications, two of which are illustrated in the accompanying drawing and specifically described in the specification.

On the drawing:

Figure 1 is a diagram of a radio signal receiving apparatus in which one form of my invention is used,

Fig. 2 shows diagrammatically, a radio signalling sending apparatus in which another form of my invention is employed.

As shown in Fig. 1, an antenna 1 is supplied with a loading coil 2, an adjustable condenser 3 and a ground connection 4. Inductively related to the coil 2 is a secondary coil 5 in'shunt with which thereis an adjustable condenser 6. The tuned circuit, comprising the inductor 5 and the condenser 6, is connected at one point to the filament 7 of a vacuum-tube device 8. At another point, this circuit is connected to the grid 9 of said vacuum tube. This connection includes a grid condenser 11. The anode 13 of the vacuum tube 8 is connected to the primary coil 14 of a transformer. One terminal of the secondary coil 5 15 is connected to the filament 16 of a vacuumtube amplifier 17. The other terminal of the secondary coil 15 is connected to the grid 18 of this amplifier. The anode 19 of the amplifier 17 is connected to the telephone or other indi- 10- cating instrument 21 which is shunted by a fixed condenser 22.

These features are all of standard construction and are included in this description merely'for the sake of making a concrete example of the application of my invention. The manner of supplying energy to the filaments '7 and 16 and to the circuits including the anodes 13 and 19 constitutes a feature of my invention.

In the form illustrated in Fig. 1, an alternating current generator 23 is caused to deliver energy to a rectifying, device 24. From the rectifying device, direct current is supplied to the filaments '7 and 16 by means of conductors 25 and 26. A pilot conductor or multi-unit filteris introduced between the rectifying device 24 and the filaments. This filter includes a plurality of condensers 27, one condenser for each unit of the filter, and a plurality of inductors 28,.one inductor for each filter unit. Since the current required for heating the filament is of considerable amount and must be delivered at low voltage, the generator 23 andvrectifier 24 should be designed for delivering a fairly large current at a low potential. The number of units in the filter must be suflicient to insure that no hum, corresponding to the period of the generator 23 or to its harmonics, will occur in the telephone 21. I have found that for ordinary conditions, with a filter having an attenuation constant as large as 4, at the frequency to be eliminated, five filter units are ample to accomplish this result.

The alternating current generator 29 delivers energy to the rectifier 30. This rectifier is connected by conductors 31 and 32 to the anode circuits of the tubes 8 and 1'7, that is to say, the conductor 31 is connected to the terminal of the primary coil 14 farthest from the anode 13 and to the terminal of the telephone 21 farthest from the anode 19. The conductor 32 is connected to the filaments 7 and 16. Between the conductors 31 and 32, and the rectifying device 30, a pilot-conductor or multi-unit filter is inserted, which consists of a number of condensers 33, one condenser for each unit of the filter, and a number of retion factor for this filter and the number of units therein should be so chosen that there will not be sufficient alternating component in the current delivered to the anode circuits to produce any perceptible hum in the telephone 21. I have found that, for ordinary circumstances, a filter Whose attenuation constant at the frequency to be eliminated is 4 and which consists of five units is sufficient for this purpose.

In Fig. 2, a sending antenna 36 is shown, having an inductor 37, a telephone transmitting instrument 38 and a ground connection 39. Two vacuum-tube devices 41 and 42 connected in parallel are part of the system for energizing the antenna 36. Filaments 43 and 44 in these thermionic devices are connected together and to the antenna at a point in the inductor 3'7, as shown at 45. Grids 46 and 47, one in each of the tubes, are connected together and to the antenna 36 near the lower end of the inductor 37 by a conductor 48. A condenser 49, shunted by a leak resistor 50, is included in the conductor 48. The anodes 51 and 52 are connected together and to a point near the upper end of the inductor 37 by a connection 53 which includes a stop condenser 54.

These details of the construction and connection of the tubes 41 and 42 and the antenna 36 were familiar features of sending apparatus before my invention, but the herein described manner of supplying energy to the anode circuits and of supplying heating current to the filament constitutes a feature of my invention.

The current for the filaments is supplied from a direct current generator 55 over conductors 56 and 57. The connection between the generator 55 and these conductors includes a filter comprising condenser 58 and inductors 59. These inductors preferably have laminated iron cores with fairly long air gaps. The filter is designed to have an attenuation constant of about 4, at the commutation frequency, and comprises as many filter units, each comprising an inductor 59 and a condenser 58, as are necessary to insure that no hum, due to the commutator of the generator 55, will be heard in the telephones of the receiving systems, affected by the energy delivered from the antenna 36. I have found that ordinarily five filter units are sufiicient for this purpose.

-sistors 34, one for each filter-unit. The attenua- The anode circuits are energized by a direct current generator 60 which is connected by a conductor 61 to the conductor 53 joining the anodes and by a conductor 62 to the conductor 56 joining the filaments. Between conductors 61 and 62 and the generator 60 a filter is inserted. Preferably this is an aperiodic filter, each unit of which consists of a condenser 63 and a resistor. 64. The attenuation factor of this filter and the number of units therein must be so chosen that the energy delivered to the anode circuits will not cause a hum in the telephones, due to the commutator of the generator 60. I have found that ordinarily, with an attenuation factor of 4, five filter-units is an abundant protection against such a hum.

The commutator frequency of the generators 55 and 60 should be high, in order that the filtering action shall be effective; but, except for an increased number of commutator segments, these machines are of standard type. If desired, the two machines may be combined into one generator, having a single armature and two commutators, with the windings'connected to one commutator arranged for delivering a small current at a high potential and the windings connected to the other commutator arranged for delivering a larger current at a smaller potential. When separate machines are used, of course, they should be designed in accordance with the work they have to perform, that is, the generator 60 should be designed to deliver a small current at a high potential, while the generator 55 should be designed to deliver a larger current at a lower potential.

. It will be obvious to those skilled in the art that numerous variations in the details of construction and in the connections may be made without departing from the spirit of this invention and I, therefore, do not intend to limit the patent granted except as is required by the prior art or indicated in the claim.

1 claim as my invention:

A radio system adapted for use from power mains comprising in combination a plate circuit, a filament circuit and means for by-passing audio frequency oscillations between the terminals of the filament circuit comprising a large capacity condenser connected across the filament terminals.

MICHAEL I. PUPIN. 

